The present invention relates to image signal converters converting each of component video signals of different scanning formats to be supplied to a display device such as a television receiver into signals of a common scanning format.
A schematic structure of a conventional image signal converter incorporated in a television receiver such as a high-definition TV is shown in FIG. 8. A conventional image signal converter ICc includes an input terminal 1, a color-difference signal demodulator 2, a selector 3, a sync separator 4, an RGB processor 5, and a display 6.
The input terminal 1 receives a first component video signal Scv1 including a luminance signal Y, a color-difference signal PB and a color-difference signal PR outputted from an external video/audio data source, typically a digital television STB (Set-top Box) or DVD player. The input terminal 1 then supplies each of the luminance signal Y, the color-difference signal PB and the color-difference signal PR included in the first component video signal Scv1 to the selector 3.
The color-difference signal demodulator 2 generates a second component video signal Scv2 composed of a luminance signal Y, a color-difference signal U (=Bxe2x88x92Y), and a color-difference signal V (=Rxe2x88x92Y) from a luminance signal Y and a chroma signal C obtained based on a composite video signal of any television standard system (in this example, the NTSC system). The luminance signal Y, the color-difference signal U and the color-difference signal V (Rxe2x88x92Y) of the second component video signal are each supplied to the selector 3. Note that the luminance signal Y and the chroma signal C to be supplied to the color-difference signal demodulator 2 are obtained from, for example, an NTSC composite video signal supplied by a Y/C separator (not shown) after Y/C separation or an output from the so-called S terminal of a video tape recorder.
The selector 3 selectively outputs either the first component video signal Scv1 (Y, PB, PR) from the input terminal 1 or the second component video signal Scv2 (Y, U, V) from the color-difference signal demodulator 2. Note that this selection of the component video signal is made by the selector 3 based on a selecting signal Sw externally provided.
The sync separator 4 is implemented by a sync separator circuit, which separates and extracts a horizontal synchronization signal H-SYNC and a vertical synchronization signal V-SYNC from the luminance signal Y included in the first or second component video signal Scv1 or Scv2 supplied by the selector 3.
The RGB processor 5 is implemented by an RGB demodulator circuit, which demodulates the first component video signal Scv1 Y, PB, PR) or the second component video signal Scv2 (Y, U, V) and outputs the original color signals of R, G, and B.
An image is displayed on the display 6 based on the each of the color signals R. G, and B received from the RGB processor 5.
The operation of image signal conversion by the above image signal converter ICc is briefly described below. A user operates a remote controller (not shown) to supply the selector 3 with the selecting signal Sw for providing an instruction of selecting either the first or second component video signal Scv1 or Scv2 and outputting the selected component video signal to the RGB processor 5.
When the external device such as a digital television STB and DVD player is connected to the input terminal 1, the selector 3 outputs the first component video signal Scv1 received from the input terminal 1 based on the selecting signal Sw. Otherwise, the selector 3 outputs the second component video signal Scv2 received from the color-difference signal demodulator 2 based on the selecting signal Sw.
The first component video signal Scv1 (Y, PB, PR) supplied to the input terminal 1 is outputted to the selector 3 without any processing. If supported by an NTSC interlaced scanning format of approximately 480 valid display scanning lines per frame (hereinafter referred to as xe2x80x9c480i formatxe2x80x9d), the first component video signal Scv1 (Y, PB, PR) is supplied to the RGB processor 5 through the selector 3. Note that the luminance signal Y included in the first component video signal Scv 1 is supplied also to the sync separator 4.
On the other hand, when the video signal of the NTSC 480i format is supplied to the color-difference signal demodulator 2 in a state that its luminance signal Y and chroma signal C have already been separated, the color-difference demodulator 2 demodulates these incoming signals and then outputs the second component video signal Scv2 composed of the luminance signal Y and the color-difference signals U and V. In this case, as described above, the selector 3 is switched in advance so as to output the second component video signal Scv2 received from the color-difference signal demodulator 2. The second component video signal Scv2 is supplied through the selector 3 to the RGB processor 5, and the luminance signal Y included therein is supplied to the sync separator 4.
The sync separator 4 separates and extracts the horizontal synchronization signal H-SYNC and the vertical synchronization signal V-SYNC from the received luminance signal Y. These extracted synchronization signals H-SYNC and V-SYNC are supplied to a deflector (not shown) in the display 6.
The RGB processor 5 demodulates the first component video signal Scv1 (Y, PB, PR) or the second component video signal Scv2 (Y, U, V) to obtain original color signals of R, G, and B. These demodulated color signals are supplied to the display 6.
As such, when the first component video signal of the 480i format is supplied by the input terminal 1, or when the luminance signal Y and the chroma signal C of the 480i format are supplied to the color-difference signal demodulator 2, a color image can be displayed on the display 6.
However, in the image signal converter ICc, if a video signal of a scanning format other than the 480i format is supplied to the input terminal 1 as the first component video signal Scv1 (Y, PB, PR), it is impossible to correctly display a color image of the first component video signal Scv1 supplied to the display 6.
For example, in some cases, the first component video signal Scv1 (Y, PB, PR) is supported by a progressive scanning format of approximately 480 valid display scanning lines per frame (hereinafter referred to as xe2x80x9c480pxe2x80x9d format). Since being a non-interlaced scanning, the progressive scanning format is different from the 480i format in the number of valid display scanning lines per field. Therefore, the display 6 cannot display an image of the 480p first component video signal Scv1 supplied to the RGB processor 5 based on the horizontal and vertical synchronization signals H-SYNC and V-SYNC extracted by the sync separator 4.
As such, in the image signal converter ICc, the image of the first component video signal Scv1 cannot be correctly displayed except when the input signal is compliant with the 480i format. Therefore, the scanning format of the first component video signal Scv1, which is an output from the external device connected to the input terminal 1, is severely limited.
In the long run, in digital television STBs and DVD players, it is expected that component video signals Scv of a plurality of types of scanning formats such as the 480i and 480p formats will be supplied thereto by the same output terminal for providing users with video of various image qualities. The image signal converter ICc, however, cannot meet such expectations.
An object of the present invention is to provide an image signal converter that converts each scanning format of incoming component video signals Scv of a plurality of types of scanning methods from external devices such as digital television STBs and DVD players for correct image display are supplied thereto.
Further, another object of the present invention is to provide an image signal converter that can also support a case in which a luminance signal and a chroma signal obtained based on a composite video signal of a television standard system such as the NTSC system.
To achieve the above objects, the present invention has the following aspects.
A first aspect of the present invention is directed to an image signal converter converting a component video signal of an interlaced scanning format into a signal of a progressive scanning format to display an image on a display device supporting the progressive scanning format. The present invention in accordance with the first aspect comprises an up-converter for up-converting the component video signal of the interlaced scanning format into a signal of the progressive scanning format, a scanning format determination part for determining whether a scanning format of the component video signal is the interlaced scanning format or the progressive scanning format based on a luminance signal included in the component video signal, and an output destination selector for selecting an output destination of the component video signal based on determination of the scanning format determination part. When the scanning format determination part determines that the scanning format is the interlaced scanning format, the component video signal is outputted to the up-converter.
As described above, in the first aspect of the present invention, even if the component video signal of the interlaced scanning format is inputted, such signal is automatically up-converted to a signal of the progressive scanning format, and an image can be appropriately displayed.
According to a second aspect of the present invention, further to the first aspect, the image signal converter further comprises a sync separator for extracting a vertical synchronization signal and a horizontal synchronization signal from the luminance signal included in the component video signal and a sync generator for generating an up-conversion-purpose horizontal synchronization signal and an up-conversion-purpose vertical synchronization signal that are referred to when the up-converter up-coverts the component video signal, based on the extracted horizontal synchronization signal.
According to a third aspect of the present invention, further to the first aspect, the component video signal includes a first component video signal comprising a luminance signal and color-difference signals of two types and a second component video signal comprising a luminance signal and color-difference signals of two types obtained by demodulating a luminance signal and a chroma signal based on a composite video signal of a plurality of television standard systems.
According to a fourth aspect of the present invention, further to the first aspect, the image signal converter further comprises a detector detecting whether the number of scanning lines of the component video signal has been previously assumed. When the detector detects that the number of scanning lines has not been previously assumed, the sync generator generates free-running horizontal and vertical synchronization signals each having a predetermined frequency compliant with the progressive scanning format instead of the vertical synchronization signal and horizontal synchronization signal to prevent synchronization from being unstable on a display screen of the display device.
As described above, in the fourth aspect of the present invention, when an irregular component signal is inputted, image display is made based on a synchronization signal having a predetermined frequency irrespectively of the irregular component signal, thereby protecting the display device.
According to a fifth aspect of the present invention, further to the fourth aspect, the image signal converter further comprises an on-screen display displaying on-screen that the component video signal is invalid when the detector detects that the number of scanning lines has not been previously assumed.
According to a sixth aspect of the present invention, further to the fifth aspect, the detector detects frequencies of the vertical synchronization signal and horizontal synchronization signal extracted by the sync separator and the on-screen display displays the detected frequencies of the vertical synchronization signal and horizontal synchronization signal or the number of scanning lines corresponding thereto when the detector detects that the number of scanning lines has not been previously assumed.
As described above, in the sixth aspect of the present invention, notification of specific information of an irregular input in real time enables the user to take quick and appropriate action.
A seventh aspect of the present invention is directed to a display device for a component video signal image in which the image signal converter in the first through sixth aspect is incorporated.
An eighth aspect of the present invention is directed to a method of converting a component video signal of an interlaced scanning format into a signal of a progressive scanning format to display an image on a display device supporting the progressive scanning format. The invention in accordance with the eighth aspect comprises up-converting the component video signal of the interlaced scanning format into the signal of the progressive scanning format, determining whether a scanning format of the component video signal is the interlaced scanning format or the progressive scanning format based on a luminance signal included in the component video signal and selecting an output destination of the component video signal based on the scanning format determination. When it is determined that the format is the interlaced scanning format, the component video signal in the output destination selection is up-converted.